The overall objective of this research project is the elucidation of the organization of genetic elements in the eukaryote chromosome concerned with the time specific and tissue specific regulation of gene activity during development. Specifically, we propose to induce, recover, and characterize high and low activity, time specific, and tissue specific regulator mutants in contiguous control elements of gene for dopa decarboxylase (DDC) in Drosophila melanogaster. These contiguous regulator mutants will be subjected to high resolution mapping to establish that the lesions are in regions outside the structural element, to determine if the different types of regulator mutants are clustered, and if so to determine the positions of the clusters relative to one another. When such contiguous regulator mutants have been mapped, studies on the altered DNA sequences will be initiated on gene specific DNA isolated and amplified by recombinant plasmids. In addition, studies on non-contiguous DDC regulator mutations and suppressors of contiguous regulator mutations will be initiated to identify those effector molecules which interact with control elements in the DDC structural gene.